Intraspecific Variation in Reproductive Behavior and Morphology in the Male Intraspecific Variation in Reproductive Behavior and Morphology in the Male Green Anole LizardGreen Anole Lizard

((Anolis carolinensis)Anolis carolinensis)Joseph R. VandecarJoseph R. Vandecar11, Michele A. Johnson, Michele A. Johnson22, Rachel E. Cohen, Rachel E. Cohen22, Juli Wade, Juli Wade1,21,2

Departments of Departments of 11Psychology and Psychology and 22Zoology, Michigan State UniversityZoology, Michigan State University

MethodsMethods

ResultsResults

Future DirectionsFuture Directions

Larger reproductive structures exist in males with increased levels of behavior.

Acknowledgements Acknowledgements

Funded by Ronald E. McNair Post-Baccalaureate Achievement Program/Summer Opportunity Research Program, Michigan State University, East Lansing, MI and the National Science Foundation

Acknowledgements : Nancy Walters, Jean Lafitte National Park and Preserve, National Park Service; Louisiana Department of Fish & Wildlife; Danny Horton, Michelle Tomaszycki, Kenneth Sands, Parth Tikiwala

Correspondence: Joseph Vandecar, jrvandecar@yahoo.com

To determine relationships between courtship behavior and morphology of reproductive structures in adult male green anole lizards.

•Measure the muscles that control copulatory behaviors (use of the two penises, hemipenes). •Add six more adult males into our sample size.•Examine the motoneurons that innervate the muscle that controls the movement of the hemipenes. •Investigate courtship and copulatory structures and behaviors in females.

•Focal behavioral observations of 12 adult males were conducted in the Jean Lafitte National Park and Preserve in southern Louisiana during the breeding season (May 2008).

•Animals were collected and rapidly decapitated after 90-180 min behavioral observations. Tissues were frozen on dry ice and returned to MSU where they were stored at -80oC.

•Tissues were cut at 20µm, stained with hematoxylin and eosin, and measured using Scion Image software.

•Cross-sectional areas were measured from the following structures :

-Testes – semeniferous tubules

-Kidneys – renal sex segment

- Ceratohyoid muscle fibers (Fig.1)

Why Anoles? Green anoles are an ideal animal model for the study of reproductive behavior and morphology. Unlike many bird and mammalian models, this lizard species exhibits both courtship and copulatory behaviors that are easily observable by researchers. Courtship consists of three displays: head-bobs, push-ups, and extensions of a throat fan (dewlap). While these display behaviors are stereotyped, display rates vary within each species.

(1) The reproductive structures, together, influenced a large proportion (60%) of display behavior. However, the lack of significant relationships between the morphology of individual components and level of function might suggest that displays require their collective influences. This idea contrasts with data from green anoles in the lab, in which ceratohyoid fiber size is positively correlated with dewlap extension (Neal and Wade, 2007).

(2) Negative relationships between seminiferous tubule size and both display time and muscle fiber size could be due to either: (a) a “trade-off” such that resources are selectively allocated; or (b) increased testis size might result in enhanced reproductive capacity independent of courtship behavior.

(3) The positive correlations between overall size of the dewlap (cartilage length) and display of behavior parallels previous findings from this and other anole species (Vanhooydonck, 2005), and is consistent with the idea that increased benefits are provided by use of larger dewlaps.

PurposePurpose DiscussionDiscussion

Introduction Introduction

PredictionPrediction

Figure 1: The ceratohyoid muscle controls dewlap extension. From Wade, 2005.

Figure 2. Negative relationships exist between testis morphology and both courtship behavior and size of the muscle fibers that control it

Model R2 df F β pOveral

l0.602 3,8 4.03 - 0.05

Kidney - - - 0.52 0.07Testis - - - -0.45 0.17Muscl

e- - - 0.21 0.53

Overall dewlap size (cartilage length) was positively correlated with dewlap use (R= 0.75, p = 0.005). No relationships were found between ceratohyoid fiber size and the display time or length of the associated ceratobranchial cartilage. Body size was not correlated with any measure of reproductive morphology.

Table 1. A multiple regression indicated that, overall, reproductive morphology predicted display rate. However, individual components did not show significant relationships with behavior.

Dewlap

CopulationCourtship